The airborne missile with attitude-orbit controlled impetus motor can head off the target in farther area and earlier occasion, even out of defense region. The project of solid propellant rocket engine with multi-nozzle was implemented, and the paper put importance on the investigation of interior ballistics characteristic. By analyzing the influencing factors, the parameter distributing law on internal flow field was analyzed and summarized. The result shows that the impetus motor can work normally and the internal flow field is symmetrical, but there is some interference in these nozzles. The working performance of impetus motor is validated in examination.